We show some thermodynamic results concerning chemical kinetics, either from statistical physics, under the strong assumption (EXS) of the statistical exponential distribution of the physical states, or from kinetics. In that frame, the reaction rates are modeled according to the stochastic activation collision theory, under the weaker assumption (EXW) of the statistical exponential distribution not on the whole space but only within each structure; moreover a symmetry condition (SY) concerning the local properties of the rate constants is assumed. The Boltzmann distribution and an extension of the more general result of the thermodynamic law of mass action are proved. Moreover, we show that the assumptions (EXS) and (EXW) are equivalent, under (SY). At last, we deal with the stochastic example of the RNA structure for which we calculate the temporal probabilities of the structures by means of a jump process. (C) 1997 American Institute of Physics.